Recent developments in solid state radar have revealed the advantage of utilizing a “lattice” type of structure for fabricating radar arrays in which horizontally oriented rows and vertically oriented columns interlock to form a stiff, strong array skeleton. When external thin, flat plates (referred to as “skins”) are attached to the front and rear of this lattice, the resultant structure has a very high stiffness to weight ratio, much like a honeycomb panel. A high stiffness-to-weight ratio enables fabrication of lightweight array structures which are desirable for today's land, sea, and air based radar platforms.
An example of such an array skeleton is shown in FIG. 1. As can be seen, the array skeleton 1 includes a plurality of row members 2, a plurality of column coldplate members 4, a T/R coldplate 6 backing the row/array structures, and a radiator coldplate 8 disposed adjacent to the T/R coldplate 6. FIG. 2 is an isometric view of the rear of an octagonal array antenna “AT” illustrating a plurality of array skeletons “AS” populated with electronic elements. The radiating face of antenna “AT” of FIG. 2 is the side opposite to the illustrated side. FIG. 2 also illustrates a populated array skeleton “AS” broken away from antenna “AT”. Populated array skeleton “AS” is thus a portion of, or a subset of a plurality of similar populated skeletons or lattices which together make up a portion of antenna array “AT.” In FIG. 2, the rear portion of the populated array skeleton “AS” is closed by a plurality of electronic enclosure doors.
The row and column members 2, 4 utilized in typical array skeleton arrangements are slotted 10 at each row/column interface (FIG. 3A), such that they seat within each other when assembled (FIG. 3B). The disadvantage of such an arrangement, however, is that membrane forces are translated only along the back half “BH” of the column members 4 and the front half “FH” of the row members 2.
Other designs employ “L” brackets 12, (see FIG. 4) attached with mechanical fasteners (e.g., screws), and positioned at the interface between each row and column member 2, 4. The “L” brackets 12 provides the arrangement with increased stiffness because they allow membrane forces to be supported along the entire depth “D” of each row/column joint 14. While this approach provides a sound structural interface, it adds structure weight due to the numerous L-brackets 12 and fasteners. Furthermore, this approach adds significant cost to the array structure, both in materials and in touch labor. Significant assembly labor costs are associated with having to install the numerous fasteners. Further exacerbating this problem is the fact that these L-brackets 12 must be installed within the confined cavities formed by the interlocking rows/columns. Finally, the number of row/column interfaces 14 present in typical shipboard and land based arrays number in the hundreds, and can exceed 1000, depending on the size of the array aperture. Thus, the costs (material and installation labor) and weight associated with these L-brackets 12 can be significant.
To realize the full mechanical advantage (i.e. high stiffness/weight ratio) of the lattice structure, these row/column interfaces should be secured such that forces are translated continuously across the entire depth of each row/column, and thus subsequently along the length of each row/column. Thus, there is a need for an improved and simplified design for row/column interfaces that result in a high strength, high stiffness, joint, without the equipment and installation expense required of present high strength designs.